Plasma reactor with heated source of a polymer-hardening precursor material

ABSTRACT

A general method of the invention is to provide a polymer-hardening precursor piece (such as silicon, carbon, silicon carbide or silicon nitride, but preferably silicon) within the reactor chamber during an etch process with a fluoro-carbon or fluoro-hydrocarbon gas, and to heat the polymer-hardening precursor piece above the polymerization temperature sufficiently to achieve a desired increase in oxide-to-silicon etch selectivity. Generally, this polymer-hardening precursor or silicon piece may be an integral part of the reactor chamber walls and/or ceiling or a separate, expendable and quickly removable piece, and the heating/cooling apparatus may be of any suitable type including apparatus which conductively or remotely heats the silicon piece.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.08/580,026 pending filed Dec. 20, 1995 by Kenneth S. Collins et al.which is a continuation of Ser. No. 08/041,796 now U.S. Pat. No.5,556,501 filed Apr. 1, 1993 which is a continuation of Ser. No.07/722,340 abandoned filed Jun. 27, 1991; and a continuation-in-part ofSer. No. 08/503,467 filed Jul. 18, 1995 now U.S. Pat. No. 5,770,099 byMichael Rice et al. which is a divisional of Ser. No. 08/138,060 filedOct. 15, 1993 now U.S. Pat. No. 5,477,975; and a continuation-in-part ofSer. No. 08/597,577 filed Feb. 2, 1996 pending by Kenneth Collins, whichis a continuation-in-part of Ser. No. 08/521,668 filed Aug. 31, 1995(now abandoned), which is a continuation-in-part of Ser. No. 08/289,336abandoned filed Aug. 11, 1994, which is a continuation of Ser. No.07/984,045 filed Dec. 1, 1992 (now abandoned). In addition, U.S.application Ser. No. 08/468,254 filed May 13, 1996 pending by Kenneth S.Collins et al. entitled "Inductively Coupled RF Plasma Reactor HavingOverhead Solenoidal Antenna" discloses related subject matter.

BACKGROUND OF THE INVENTION

1. Technical Field

The invention is related to a plasma reactor for processing a workpiecesuch as a semiconductor wafer with a process employing an etchselectivity-enhancing precursor material such as polymer precursorgases.

2. Background Art

High density RF plasma reactors for etching contact openings throughsilicon dioxide layers to underlying polysilicon conductor layers and/orto the silicon substrate of a semiconductor wafer are disclosed in theabove-referenced application by Collins et al. Ideally, such a reactorcarries out an etch process which quickly etches the overlying silicondioxide layer wherever a contact opening is to be formed, but stopswherever and as soon as the underlying polysilicon or silicon material(or other non-oxygen-containing material such as silicon nitride) isexposed, so that the process has a high oxide-to-silicon etchselectivity. Such reactors typically include a vacuum chamber, a wafersupport within the chamber, process gas flow inlets to the chamber, aplasma source coil adjacent the chamber connected to an RF power sourceusually furnishing plasma source power and another RF power sourceconnected to the wafer support usually to furnish plasma bias power. Fora silicon oxide etch process, a process gas including an etchant such asa fluorine-containing substance is introduced into the chamber. Thefluorine in the process gas freely dissociates under typical conditionsso much that the etch process attacks not only the silicon oxide layerthrough which contact openings are to be etched, but also attacks theunderlying polysilicon or silicon material as soon as it is exposed bythe etch process. Thus, a typical etch process carried out by such areactor is not the ideal process desired and has a loweroxide-to-silicon etch selectivity. As employed in this specification,the term "etch selectivity" refers to the ratio between the etch ratesof two different materials, such as silicon dioxide and silicon (eithercrystalline silicon or polycrystalline silicon hereinafter referred toas "polysilicon"). A low etch selectivity can cause punch through. Inetching shallow contact openings to intermediate polysilicon layerswhile simultaneously etching deep contact openings to the underlyingsilicon substrate, the etch process first reaches and will punch throughthe intermediate polysilicon layer before reaching the siliconsubstrate. A very high oxide-to-silicon etch selectivity is necessary toprevent the punchthrough, depending upon the ratio between the depths ofthe silicon substrate and the intermediate polysilicon layer through thesilicon oxide. For example, if (a) the deep contact opening through theoxide to the substrate is 1.0 micron deep and is to be 50% overetched,(b) the intermediate polysilicon layer is 0.4 microns deep (below thetop of the oxide layer) and (c) if not more than 0.01 microns of theintermediate polysilicon layer are to be removed (to avoidpunch-through), then an oxide-to-silicon etch selectivity of at least110:1 is required.

It is known that oxide-to-silicon etch selectivity is enhanced by apolymer film which forms more readily over silicon and polysilicon orother non-oxygen-containing layers than over silicon dioxide or otheroxygen-containing layers. In order to form such a selectivity-enhancingpolymer film, the fluorine-containing substance in the process gas is afluoro-carbon or a fluoro-hydrocarbon. Some of the fluorine in theprocess gas is consumed in chemically etching the silicon dioxide layeron the wafer. Another portion of the fluorine reacts with other speciesincluding carbon contained in the process gas to form a polymer on thesurface of the wafer. This polymer forms more rapidly and strongly onany exposed silicon and polysilicon surfaces (or othernon-oxygen-containing surfaces) than on silicon dioxide (or otheroxygen-containing surfaces), thus protecting the silicon and polysiliconfrom the etchant and enhancing etch selectivity. Etch selectivity isfurther improved by improving the strength of the polymer formed onpolysilicon surfaces. The polymer is strengthened by increasing theproportion of carbon in the polymer relative to fluorine, which can beaccomplished by decreasing the amount of free fluorine in the plasma.For this purpose, a fluorine scavenger, such as a silicon piece, can beprovided in the reactor chamber and heated to avoid being covered withpolymer and additionally to permit silicon ions, radicals and/or neutralspecies to be removed therefrom and taken into the plasma. The siliconatoms removed from the scavenger combine with some of the free fluorinein the plasma, thereby reducing the amount of fluorine available topolymerize and increasing the proportion of carbon in the polymer formedon the wafer.

While the use of a fluorine scavenger such as a heated silicon pieceinside the reactor chamber enhances etch selectivity by strengtheningthe polymer formed on the wafer, even the etch selectivity so enhancedcan be relatively inadequate for a particular application such as thesimultaneous etching of contact holes of very different depths.Therefore, it would be desireable to increase the polymer strengthbeyond that achieved by the improved scavenging technique describedabove.

Another problem is that the rate of removal of silicon from thescavenger piece required to achieve a substantial increase in polymerstrength is so great that the silicon piece is rapidly consumed and theconsequent need for its replacement exacts a price in loss ofproductivity and increased cost. Typically the scavenger piece is apiece of silicon in the reactor chamber ceiling or wall or a piece ofsilicon near the reactor chamber ceiling. The rate of removal of silicontherefrom is enhanced by applying an RF bias potential to the siliconpiece while its temperature is carefully controlled to a prevent polymerdeposition thereon and to control the rate of silicon removal therefrom.As disclosed in the above-referenced U.S. application Ser. No.08/543,067 now U.S. Pat. No. 5,809,560, silicon is added into the plasmaby a combination of applied RF bias and heating of the scavenger piece.The temperature control apparatus is integrated with the silicon pieceso that replacement of the silicon piece (e.g., a silicon ceiling) isrelatively expensive. In U.S. application Ser. No. 08/597,577 referencedabove, an all-silicon reactor chamber is disclosed in which the wallsand ceiling are silicon, and any fluorine scavenging is done byconsuming the silicon ceiling or walls, requiring their replacement atperiodic intervals with a concomitant increase in cost of operation anddecrease in productivity. Thus, not only is it desireable to increasethe polymer strength but it is also desireable to decrease the rate atwhich silicon must be removed from the scavenger to achieve a desiredetch selectivity.

SUMMARY OF THE INVENTION

It is a discovery of the invention that by raising the temperature of apolymer hardening precursor material such as silicon inside the reactorchamber beyond that required to merely scavenge fluorine--i.e., into ahigher temperature range, a different more durable polymer is formedover exposed silicon and polysilicon surfaces which is more resistant toetching than has been possible heretofore by merely scavenging fluorine.In this respect, the term "polymer hardening precursor" refers to amaterial in the chamber which, when its temperature is increased,increases the resistance to etching of the polymer formed on the waferin accordance with the temperature increase. The polymer formed byholding the polymer-hardening precursor material at the highertemperature range is more durable than polymer formed otherwise, andprotects the silicon and polysilicon surfaces so much better thatoxide-to-silicon etch selectivity is substantially enhanced over thatattained heretofore. Material from the heated polymer-hardeningprecursor (e.g., silicon) piece participates favorably in thepolymerization process by changing the process gas content ratios ofcarbon-to-fluorine, hydrogen-to-fluorine and carbon-to-hydrogen as afunction of its increased temperature, so that the resulting polymer issubstantially strengthened. As the polymer-hardening precursor piece inthe reactor chamber is heated above the polymerization temperature (thetemperature below which polymer precursor materials can condense ontothe surface) and into the higher temperature range, the etch selectivityincreases with the temperature increase. Thus, a general method of theinvention is to provide a polymer-hardening precursor piece (such assilicon, carbon, silicon carbide or silicon nitride, but preferablysilicon) within the reactor chamber during an etch process with afluoro-carbon or fluoro-hydrocarbon gas, and to heat thepolymer-hardening precursor piece above the polymerization temperaturesufficiently (i.e., into the higher temperature range) to achieve adesired increase in oxide-to-silicon etch selectivity beyond thatheretofore attained.

In accordance with an alternative embodiment of the invention, it is adiscovery of the invention that the temperature of the polymer-hardeningprecursor material can be increased even further into a maximumtemperature range at which the hardness of the resulting polymer is evengreater. In some cases, this is indicated by a shiny appearance of thepolymer. It is believed that in this maximum temperature range, materialfrom the polymer-hardening precursor piece enters into the polymer toachieve the extremely hard polymer. For example, if thepolymer-hardening precursor material is silicon and is held at thismaximum temperature range, then the resulting polymer on the wafercontains silicon.

The higher temperature range of the first embodiment and the maximumtemperature range of the second embodiment depend upon the RF biasapplied to the polymer-hardening precursor piece. In the absence of anexternal applied RF bias or potential on a polymer-hardening precursorpiece of crystalline silicon, the higher temperature range was about100° C. to about 220° C. while the maximum temperature range was above220° C. and preferably between 300° C. and 700° C. However, any directlyor indirectly applied RF bias power quickly shifts such temperaturerange downwardly.

The polymer-hardening precursor (e.g., silicon) piece may be an integralpart of the reactor chamber walls and/or ceiling. However, it ispreferably a separate, expendable and quickly removable piece, and theheating/cooling apparatus may be of any suitable type includingapparatus which conductively or remotely heats the polymer-hardeningprecursor piece. Alternatively, if plasma heating of thepolymer-hardening precursor piece is sufficient, the desired effect isachieved by refraining from cooling the polymer-hardening precursorpiece so as to maintain it at least in the higher temperature range(i.e., above the polymerization temperature). In this alternative mode,the requisite heating of the polymer-hardening precursor piece isaccomplished by exploiting plasma heating in lieu of conduction heatingapparatus mechanically coupled to the polymer-hardening precursor piece.

In accordance with a preferred embodiment of the invention, no heatingapparatus is directly or mechanically coupled to the polymer-hardeningprecursor piece, thereby permitting the piece to be cheaply fabricatedand quickly removable from the reactor chamber. In this form, thepolymer-hardening precursor piece is a simply-shaped expendable item inthe reactor chamber separate from the chamber structural features suchas the wall and ceiling, and has no mechanical features for coupling toother apparatus such as heating devices. Preferably, the heatingapparatus heats the polymer-hardening precursor piece by radiation orinduction rather than conduction to avoid mechanical coupling therewith,so as to be unaffected by removal and replacement of the expendablepiece and so as to be free from temperature sensitivity to mechanicalconnections. Also, where cooling of the silicon piece is required, it ispreferred to employ radiant cooling to avoid mechanical coupling.Similarly, temperature control is achieved by remotely (e.g., byre-radiation as with an optical pyrometric temperature probe or bystimulated emission as with a fluoro-optical temperature probe) sensingthe silicon piece temperature, so that no temperature sensor apparatusis mechanically coupled to the silicon piece. Thus, a preferredembodiment employs radiant (or inductive) heating, radiant cooling, andremote temperature sensing of the polymer-hardening precursor piece toeliminate sensitivity of the temperature control to mechanical contact.

Remote temperature sensing of the polymer-hardening precursor piece canbe performed using devices such as an optical pyrometer or afluoro-optic probe. An advantage of the latter is that it is independentof the thermal emissivity of the material being measured.

In one aspect of the invention, the silicon piece functions not only asa polymer hardening precursor material but also as a shield between theheat source and the plasma source region preventing the heat source(e.g., a radiant or inductive heater) from generating plasma. It alsoshields the heat source (or its window) from exposure to the plasma orits corrosive effects.

In a preferred implementation, the expendable polymer-hardeningprecursor piece is a planar silicon annulus or base plate extendingradially outwardly from a circumferential periphery of the wafer supportor wafer chuck toward the chamber sidewall. (Further, if desired thesilicon base plate may serve as a heat shield to protect from the plasmaan underlying ceramic clamp (or electrostatic chuck) holding the waferon the wafer pedestal used in certain types of plasma reactors.) In thepreferred implementation, the silicon base plate is heated throughinductive heating by an underlying inductor, although any other suitableremote heating technique may be employed, such as infrared radiationheating. For this purpose, silicon material of an appropriateresistivity is selected for the heated silicon piece to assure efficientinductive heating thereof by the underlying inductor and at least nearlycomplete absorption of the induction field so that the silicon piecefunctions as a plasma shield as well as a heat shield. The temperaturecontrol system monitors the silicon base plate temperature using aradiant temperature sensor facing the silicon piece through a radiantlytransparent window, or through a window which is at least nearlytransparent at a wavelength range within which the temperature sensorresponds. In one implementation, the radiantly transmissive window isquartz, the sensor is an optical pyrometer, and a small black-bodyradiator piece or gray-body radiator piece, such as a small piece ofsilicon nitride, is bonded to a location on the silicon base plateviewed by the temperature sensor to enhance the sensor's performance.

If the present invention is employed (for example, in the form of theradiantly heated silicon baseplate) in the all-silicon reactor chamberof U.S. application Ser. No. 08/597,577 referred to above, then thewalls of the all-silicon reactor are operated in a "light deposition"mode rather than in an etch mode so as to not consume (or at least toreduce the rate of consumption of) the silicon side wall or skirt andthe silicon ceiling. Thus, what is chiefly consumed is the inexpensiveand quickly replaceable silicon base plate. This is best accomplished byreducing the temperature of the silicon side wall or skirt and siliconceiling and reducing or eliminating the RF bias applied thereto (e.g, bygrounding the wall, skirt and/or ceiling). Preferably, the temperatureof the silicon wall and silicon ceiling and the RF bias thereon isreduced to a point at which consumption thereof is minimized bypermitting a light polymer deposition thereon, but not beyond a point atwhich polymer deposition thereon becomes dense and difficult to remove.Such a lightly deposited polymer can be quickly and easily removed by aplasma clean step. This preserves a major advantage of the all-siliconreactor chamber in avoiding or minimizing the necessity of frequentchamber cleanings, as described in the above-referenced application.Alternatively, but not preferably, a "heavy deposition model" may beselected which permits a heavy polymer deposition onto the silicon walland ceiling.

In accordance with another embodiment of the invention, separatelyexpendable silicon pieces are disposed at different radial locationsrelative to the wafer being processed in order to enable independentcontrol of etch selectivity over different radial portions of the wafer.This embodiment may be combined with the features of separatelycontrollable inductors at respective radial locations and separatelycontrollable electrodes at respective radial locations disclosed inco-pending U.S. application Ser. No. 08/597,577 referred to above.

It is a further discovery of the invention that the polymer-hardeningprecursor function fulfilled by the silicon piece requiring the elevatedtemperature described above does not imply a concomitantly elevatedconsumption rate. Where the silicon piece is not an expendable item inthe reactor (or even if it is), its rate of consumption can be reducedto save cost while preserving its polymer-hardening function above thepolymerization temperature. This is accomplished by reducing the RF biasapplied to the silicon piece while further increasing the temperaturethereof to compensate for the decrease in RF bias and thereby maintainits polymer-hardening participation in the process. In accordance withone implementation, the RF bias thereon can be decreased four-fold for adramatic decrease in consumption rate while increasing the silicon piecetemperature by only about 25% to maintain the polymer-hardeningfunction. Preferably, the temperature is increased until the applied RFbias can be eliminated entirely.

While the preferred material employed in the various embodiments of thepolymer-hardening precursor referred to above is silicon, any othersuitable material whose contribution to the polymer hardness is achievedby heating a piece of it in the reactor may be employed in the foregoingembodiments. In addition to silicon, other suitable polymer-hardeningprecursor materials include silicon carbide, carbon and silicon nitride.Thus, the invention is more generally directed to heating apolymer-hardening precursor material of the type including silicon to atleast a higher temperature range (above the polymerization temperature).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified cut-away side view of a plasma reactor of thetype disclosed in a first one of the co-pending applications referred toabove.

FIG. 2 is a simplified cut-away side view of a plasma reactor of thetype disclosed in a second one of the co-pending applications referredto above.

FIG. 3 is a simplified cut-away side view of a plasma reactor of thetype disclosed in a third one of the co-pending applications referred toabove.

FIG. 4A is a cut-away side view of a plasma reactor in accordance with apreferred embodiment of the present invention employing inductiveheating of an expendable polymer-hardening precursor piece.

FIG. 4B is an enlarged cross-sectional view of the workpiece processedin a working example of the embodiment of FIG. 4A, illustrating themulti-layer conductor structure of the workpiece.

FIG. 4C is an enlarged view corresponding to FIG. 4A illustrating asleeve and counterbore in which an optical fiber is inserted.

FIG. 4D is an enlarged view corresponding to FIG. 4A illustrating a longwavelength optical window inside a heat transparent window.

FIG. 4E is an enlarged view corresponding to FIG. 4A illustrating a longwavelength window separate from a heat transparent window.

FIG. 5A is a graph illustrating oxide-to-silicon etch selectivity as afunction of temperature of a polymer-hardening precursor ring.

FIG. 5B is a graph illustrating radial distribution of the polysiliconetch rate in angstroms/minute at temperatures of 240° C. and 500° C.,respectively.

FIG. 6 is a cut-away view of a plasma reactor in accordance with anotherpreferred embodiment of the invention employing radiant or infraredheating of an expendable polymer-hardening precursor piece.

FIG. 7 is a cut-away view of a plasma reactor in accordance with apreferred embodiment of the invention in which an expendablepolymer-hardening precursor piece is heated in an all-semiconductorreactor chamber.

FIG. 8A is a cut-away side view of a plasma reactor in accordance with apreferred embodiment employing heated polymer-hardening precursor piecesat separate radial locations relative to the wafer being processed.

FIG. 8B corresponds to the embodiment of FIG. 8A in which the ceiling isdivided into inner and outer portions.

FIG. 9 illustrates an embodiment of the invention in which theexpendable polymer-hardening precursor piece is a removable linerabutting the cylindrical chamber side wall.

FIG. 10 is a graph illustrating the performance of a working example ofa temperature control system in a reactor embodying the invention.

FIG. 11 is a graph illustrating the closed loop response of thetemperature system whose performance is depicted in FIG. 10.

FIG. 12 is an enlarged view of a portion of the graph of FIG. 11.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, the above-referenced co-pending U.S. applicationSer. No. 08/580,026 discloses a plasma reactor chamber 10 having acylindrical side wall 12, a flat ceiling 14, a wafer support pedestal 16for supporting a workpiece 17 being processed such as a semiconductorwafer, an inductive side coil 18 wound around the cylindrical side wall12 and independent RF power sources 20, 22, 24 connected to the ceiling14, the pedestal 16 and the inductive coil 18, respectively. Inparticular, the co-pending application of Collins et al. discloses thatthe ceiling 14 may comprise silicon in order to provide a fluorinescavenger. For this purpose, RF power is applied to the silicon ceiling14 by the RF power source 20 to enhance the removal of silicontherefrom.

Referring to FIG. 2, the above-referenced co-pending application by Riceet al. discloses that the side wall 12 is quartz and provides atemperature control system for controlling the temperature of the quartzside wall 12 and the temperature of the silicon ceiling 14. Thetemperature control system includes a cooling source 30 and heatingsource 32 coupled to the quartz side wall 12 and a cooling source 34 andheating source 36 coupled to the silicon ceiling 14. Temperature sensors38, 40 coupled to the side wall 12 and ceiling 14, respectively, aremonitored by controllers 42, 44, respectively. The controller 42 governsthe cooling source 30 and heating source 32 of the quartz side wall 12while the controller 44 governs the cooling source 34 and heating source36 of the silicon ceiling. The purpose for controlling the temperatureof the silicon ceiling 14 is, at least in part, to prevent polymeraccumulation on the ceiling 14 which would otherwise prevent the ceiling14 from donating scavenger silicon to the plasma. Therefore, controller44 maintains the ceiling temperature somewhat above the polymercondensation (or polymerization) temperature, or about 170° C. dependingupon processing conditions. At the same time, the RF power source 20applies sufficient RF power to the silicon ceiling 14 in order promoteremoval of silicon from the ceiling 14 by the plasma at a sufficientrate to scavenge the desired amount of fluorine for enriching the carboncontent of the polymer formed on the wafer to enhance etch selectivity.In fact, the combination of elevated temperature and applied RF biasovercomes the energy threshold below which interaction between theplasma and the ceiling 14 causes polymer deposition and above which theinteraction causes etching of the ceiling 14.

Referring to FIG. 3, the above-referenced co-pending application Ser.No. 08/597,577 by Kenneth S. Collins discloses that both the ceiling 14and the side wall 12 are a semiconductor such as silicon and that theycan act as windows to permit inductive coupling of RF source powerthrough themselves to the plasma. For this reason, either one or boththe side coil 18 and an overhead inductor 50 may be employed and coupleRF source power to the plasma through the silicon side wall 12 and thesilicon ceiling 14. U.S. application Ser. No. 08/597,577 disclosed aplanar overhead coil and such would be suitable for carrying out thepresent invention. However, the overhead inductor 50 of the embodimentof FIG. 3 includes inner and outer solenoids 50a, 50b (of the typedisclosed in above-referenced co-pending U.S. application Ser. No.08/648,254 by Kenneth S. Collins et al. entitled "Inductively Coupled RFPlasma Reactor Having Overhead Solenoidal Antenna") separately poweredby independent RF power sources 52a, 52b to facilitate processuniformity control. Furthermore, both the ceiling 14 and side wall 12can be employed as separate electrodes, so that RF power is applied tothe silicon side wall 12 by a separate RF power source 54. Sufficient RFpower is applied to either or both the silicon ceiling 14 and thesilicon side wall 12 to promote removal of silicon therefrom forscavenging fluorine. The side wall 12 and ceiling 14 are preferablymaintained above the polymer condensation temperature to permit theiruse as silicon scavenger precursors and to avoid the usual requirementfor frequent chamber cleaning operations to remove polymer andassociated contaminant deposits.

A first embodiment of the present invention is a process which does notmerely enrich the carbon content of the carbon-fluorine polymer, butactually forms a different kind of polymer which more strongly adheresto the underlying silicon, polysilicon or similar non-oxygen-containingsurfaces to be protected. The result is a revolutionary improvement inetch selectivity. It is a discovery of the invention that certainmaterials in a class including silicon, silicon carbide, graphite,silicon nitride, when raised to a higher temperature range (e.g., wellabove the polymer condensation temperature) become polymer-hardeningprecursors in which they change the chemical structure of the polymer,resulting in a polymer which is far more resistant to etching than hasbeen provided in the prior art. The process is carried out bymaintaining the temperature of a polymer-hardening precursor materialinside the reactor chamber at a higher temperature range (e.g., 180° C.to 220° C. for a silicon precursor material whose potential is floatingand in any case substantially above the applicable polymer condensationtemperature). This higher temperature range varies greatly with theapplied RF bias potential on the polymer-hardening precursor materialand with the selection of the material itself.

In a second embodiment of the invention, the polymer-hardening precursormaterial is held in a maximum temperature range at which an even greaterpolymer hardness is achieved. The maximum temperature range for asilicon precursor material held at a floating potential is above 220° C.and is preferably in the range from about 300° C. to about 700° C. Thismaximum temperature range varies greatly with the RF bias applied to thepolymer-hardening precursor material. While not necessarily subscribingto any particular theory in this specification, it is felt that, in somecase but not necessarily all, at the maximum temperature range of thepolymer-hardening precursor material, the polymer-hardening precursor(e.g., silicon) material removed therefrom by the plasma bonds with thefluorine, carbon and hydrogen atoms (assuming a fluoro-hydrocarbon gasis employed) as they polymerize, the material (e.g., silicon) thus addedproviding a different kind of polymer having an optimum resistance toetching. In some cases, the polymer thus produced in this secondembodiment is distinguished by a shiny surface.

At the higher temperature range, the heated polymer-hardening precursormaterial (e.g., in the silicon ceiling 14 in the present example): (1)reduces free fluorine in the plasma by providing scavenging fluorine tothe plasma, (2) changes the relative concentrations of carbon tofluorine and hydrogen in the plasma, (3) changes the relativeconcentrations of etchant species and polymer precursor species in theplasma near the wafer surface. At the maximum temperature range, theheated polymer-hardening precursor material performs (1)-(3) above and(4) contributes polymer-hardening precursor (silicon) material into thepolymer, producing a polymer having a resistance to etching beyond whathas been heretofore attained in the art.

Efficacy of the invention is seen, for example, in the photoresistselectivity achieved by the invention, although similar improvement insilicon-to-silicon oxide selectivity is also achieved (as describedlater in this specification). When the polymer hardening precursormaterial (silicon) is heated to 300° C., sputtering effects are observedat the photoresist facets or corners of features covered by photoresist,and the etch selectivity of oxide to photoresist (the "photoresistselectivity") is only about 3:1. If the polymer hardening precursormaterial is heated further to about 430° C., then the photoresistselectivity jumps to about 5:1, a significant improvement. If thepolymer hardening precursor material temperature is increased evenfurther to about 560° C., then the photoresist selectivity increases toabout 6:1.

Carrying out the invention in the reactor chamber of FIGS. 1, 2 or 3 canbe accomplished by employing the silicon ceiling 14 or silicon side wallor skirt 12 as the polymer-hardening precursor material and increasingthe temperature of the silicon ceiling 14 of FIGS. 1, 2 or 3 (and/or thesilicon side wall 12 of FIG. 3) to the requisite temperature. Thesilicon ceiling 14 (and/or silicon side wall 12), when heated to thehigher temperature range of the present invention, becomes apolymer-hardening precursor.

One problem in using the silicon ceiling 14 (or silicon side wall 12) asa fluorine scavenger precursor is that it is consumed at a ratedetermined at least in part by the amount of RF power coupled to it andmust therefore be replaced at more frequent intervals. (RF power can becoupled to the scavenger precursor either directly from an RF powergenerator or indirectly by capacitive coupling from other chambersurfaces having RF power applied directly thereto.) Because the ceiling14 (and/or side wall 12) is integrated with the temperature controlsystem described above, its replacement entails loss of productivity dueto the amount of labor required to remove and replace it, as well as acost to acquire a new silicon ceiling 14 connectable to the temperaturecontrol apparatus. The present invention solves this problem because theprocess of the invention can further include reducing the RF biasapplied by the RF power source 20 to the ceiling 14 (or reducing the RFpower applied by the RF power source 22 to the silicon side wall of FIG.3) while further increasing the silicon ceiling (and/or side wall)temperature to compensate for the reduction in RF bias power. Theadvantage of this latter feature is that the rate at which silicon isremoved from the ceiling 14 (and/or side wall 12) is reduced with thereduction in applied RF power to the ceiling. In one example, the RFpower applied by the RF power source 20 to the ceiling 14 may be reducedfour-fold while the temperature of the ceiling 14 is increased onlymoderately from about 200° C. to about 240° C. Thus, the inventionprovides dual advantages of (a) revolutionary improvement in polymerresistance to etching and (b) reduced consumption rate of the siliconmaterial in the ceiling or side wall. The increased polymer durabilityresults in an increased etch selectivity while the decreased siliconconsumption rate results in decreased cost of operation and decreasedloss in productivity.

Even though the invention permits a reduction in consumption rate of thepolymer-hardening precursor piece (e.g., the silicon ceiling), itsreplacement is nevertheless expensive and time-consuming due at least inpart to its integration with the temperature control apparatus formaintaining the requisite temperature of the piece in accordance withthe polymer-hardening process of the present invention. However, theinvention is preferably carried out with a separate cheaply fabricatedquickly replaceable polymer-hardening precursor piece, to avoidconsuming any of the integral parts of the reactor chamber such as thechamber side wall or the chamber ceiling. Such a replaceablepolymer-hardening precursor piece can be of any suitable easilyfabricated shape (e.g., planar annulus, planar ring, solid ring,cylinder, plate, and so forth) and placed at any suitable locationwithin the reactor chamber. However, in the embodiment of FIG. 4A, theexpendable polymer-hardening precursor piece is a thin planar annularring 60 of a polymer-hardening precursor material (such as silicon)surrounding a peripheral portion of the wafer pedestal 16. While thering 60 can lie in any suitable plane within the chamber, in order topermit access to the wafer by a conventional wafer transfer mechanismthe silicon ring 60 lies slightly below or nearly in the plane of thewafer 17 held on the wafer pedestal 16.

In order to eliminate any necessity of integrating or mechanicallycoupling the polymer-hardening precursor ring 60 with a directtemperature control apparatus, heating by a method other than directconduction (e.g., radiant heating or inductive heating) is preferablyemployed. A radiant heat source such as a tungsten halogen lamp or anelectric discharge lamp may be employed. A radiant or inductive heatsource can be internal--unseparated from the ring 60, or it can beexternal--separated from the ring 60 by a transmissive window forexample. In the embodiment of FIG. 4A, an external inductive heater isemployed constituting an inductive coil 62 separated from thepolymer-hardening precursor ring 60 by a window 64 of a material such asquartz which is at least nearly transparent for purposes of inductivecoupling. In order to provide the most efficient inductive heating, thepolymer-hardening precursor ring 60 is formed of silicon having asufficiently low resistivity, for example on the order of 0.01 Ω-cm. Thefollowing is an example illustrating how to select the resistivity of asilicon version of the ring 60. If: (a) the thickness T of the ring 60must be about 0.6 cm (0.25 in) for structural-mechanical purposes, (b)the inductive heater coil 62 is driven at a frequency of 1.8 MHz, (c) anRF skin depth δ=ΓT (for example, Γ=1) is desired for optimum absorptionefficiency, and (d) the silicon ring 60 has a magnetic permeability μ,then the maximum resistivity of the silicon ring 60 is given by:

    ρ=δ.sup.2 ·π·f·μ

which in the foregoing example is 0.029 Ω-cm. The present invention hasbeen implemented using 0.01 Ω-cm silicon. In the case of a semiconductorsuch as silicon, there is no risk of falling short of the minimumresistivity in this case and so no computation of the minimumresistivity is given here.

In a working example corresponding to the embodiment of FIG. 4A, 4000Watts of source power at 2.0 MHz was applied to the inductive coil 18,1400 Watts of bias power at 1.8 MHz was applied to the wafer pedestal16, process gases of CHF₃ and CO₂ were introduced into the reactorchamber at flow rates of 120 sccm and 46 sccm, respectively, while thechamber pressure was maintained at 50 mTorr, the ceiling temperature wasmaintained at 200° C. and the side wall temperature was maintained at220° C. The polymer-hardening precursor ring 60 was crystalline siliconand reached a temperature in the range of between 240° C. and 500° C.The polymer deposited onto the silicon and polysilicon surfaces on thewafer 17 was characterized by the shinier appearance of a polymerhardened by the process of the present invention.

The semiconductor wafer 17 processed in this working example had themulti-layer conductor structure illustrated in FIG. 4B consisting of asilicon substrate 17a, a silicon dioxide layer 17b and a polysiliconconductor line 17c, the etch process being facilitated by a photoresistlayer 17d having mask openings 17e, 17f defining the openings 17g, 17hetched through the silicon dioxide layer 17b down to the polysiliconconductor 17c and the substrate 17a, respectively. A very highoxide-to-silicon etch selectivity is necessary to prevent thepunchthrough, depending upon the ratio between the depths of the siliconsubstrate and the intermediate polysilicon layer through the siliconoxide. For the case in which the deep contact opening 17h through theoxide to the substrate is 1.0 micron deep and is to be 50% overetched,the intermediate contact opening 17g to the polysilicon layer is 0.4microns deep and not more than 0.01 microns of the intermediatepolysilicon conductor layer 17c are to be removed (to avoidpunch-through), then an oxide-to-silicon etch selectivity of at least110:1 is required.

By increasing the temperature of the silicon ring 60 over the processingof successive wafers, it was found that oxide-to-silicon etchselectivity generally increased with temperature in the mannerillustrated in the graph of FIG. 5A. The two data points A and B of FIG.5A correspond to the curves A and B of FIG. 5B illustrating radialdistribution of the polysilicon etch rate in angstroms/minute attemperatures of 240° C. and 500° C., respectively. The etchselectivities of data points A and B of FIG. 5A were computed from theoxide etch rate of 9,000 angstroms/minute observed at both temperaturesas an etch selectivity of 30:1 at 240° C. and 150:1 at 500° C. Thus,increasing the temperature to 500° C. provides a selectivity well-abovethe 110:1 minimum selectivity required in the above-given workingexample of FIG. 4B.

In the embodiment of FIG. 4A, the temperature of the polymer-hardeningprecursor ring 60 is sensed by a temperature-sensing device 66 which isnot attached to the silicon ring 60. A controller 68 governing thecurrent or power flow through the inductor 62 monitors the output of thetemperature-sensing device 66 in order to maintain the temperature ofthe polymer-hardening precursor ring 60 at the desired temperature.Preferably, the temperature-sensing device 66 is a radiant temperaturesensor which responds to radiation from the ring 60 within a particularwavelength range. Such a radiant temperature sensor may be an opticalpyrometer responsive to thermal radiation or a fluoro-optical probewhich responds to optical pulse-stimulated emission. For this purpose,the window 64 is of a material which is at least sufficientlytransmissive within the wavelength range of the sensor 66 to provide anoptical signal-to-noise ratio adequate to enable temperature control ofthe ring 60. Preferably, and in addition, the material of the window 64(over its range of operating temperatures) does not thermally radiatestrongly (relative to the radiation from the silicon ring 60) within thewavelength range of the sensor 66, so that the radiation of the window64 is practically invisible to the sensor 66 so as to not interfere withits measurement of the silicon ring temperature.

If the polymer-hardening precursor ring 60 is silicon, then onedifficulty in measuring its temperature by an optical pyrometer is thatthe thermal emissivity of silicon varies with temperature. (The siliconemissivity also happens to vary with wavelength and doping level,although it is the temperature dependence of the emissivity that isaddressed here.) One solution to this problem is to bond a small piece70 of a black-body or gray-body radiating material such as siliconnitride to the ring 60. Preferably an optical fiber 72 (indicated indashed line) is placed with one end 72a facing a sensing portion 74 ofthe sensor 66 and the other end 72b facing the gray-body radiator piece70 bonded to the ring 60. (If a black-body or gray-body radiatingmaterial is not added, then the long-wavelength radiation emitted by thesilicon ring 60 at lower (e.g., room) temperatures can be carried by theoptical fiber 72 provided the fiber 72 is a long wavelength materialsuch as sapphire or zinc selenide in lieu of the usual optical fibermaterial of quartz.) Since the temperature measurement by the sensor 66can be degraded by background radiation from the plasma, it is preferredto provide a counter-bore 60a in the ring 60 to shield the optical fiberend 72b from background radiation (e.g., from heated chamber surfacesand from the plasma itself) without requiring any contact between theoptical fiber 72 and the ring 60. In addition to or instead of providingthe counter-bore 60a to shield the optical fiber end 72b from plasma orbackground radiation, the wavelength of the sensor 66 can be selected tolie outside the plasma emission band (4 microns to 8 microns). Theoptical fiber 72 may be employed with or without the gray-body radiatorpiece 70. The window 64 passes heat to the ring 60 while the opticalfiber 72 passes emission from the ring 60 to the temperature sensor 66.

If the temperature measurement is made directly of the silicon (i.e.,without the intervening gray-body radiator piece 70), then it ispreferable to use a material such as sapphire for the optical fiber 72which is highly transmissive at the emission wavelength of silicon, andto shield the optical fiber 72 with an opaque shield. Moreover, theproblem of the silicon's emissivity varying with temperature may beameliorated as shown in FIG. 4C by providing, in registration with thecounterbore 60a, a hole 60b which is a relatively deep and narrow with ahigh (e.g., 5:1) aspect ratio, the optical fiber 72 being sunk into thecounterbore 60a to prevent background optical noise from entering thefiber end and an opaque shield 72c surrounding the remainder of theoptical fiber 72. Such a deep hole may extend axially in the siliconring 60 but preferably it extends radially from the circumferential edgeof the silicon ring 60. In this implementation, virtually none of theoptical radiation from a heater lamp or from the plasma itself can enterthe optical fiber 72 to interfere with the temperature measurement.

If the ring temperature is to be sensed through the window 64 in theabsence of the optical fiber 72, then another difficulty with measuringthe temperature of the silicon ring 60 is that below 200° C. its peakthermal emission wavelength is shifted to a very long wavelength, welloutside the optical passband of typical materials such as quartz thatcan be used for the window 64. Quartz typically is transparent betweenabout 300 nm and 3 microns, while silicon's peak thermal emissionwavelength varies from 4 microns at 400° C. to 10 microns at roomtemperature. Thus, the range of directly measurable the silicon ringtemperatures is limited, since silicon below about 200° C. does notappreciably radiate within the optical passband of quartz. One solutionillustrated in FIG. 4D is to employ a small port 64a within the quartzwindow 64, the small port 64a being of a material which is transparentat the long wavelengths emitted by silicon at cooler temperatures downto room temperature. The small port 64a can be sapphire or zincselenide. The radiant temperature sensor 66 would be selected to beresponsive at the longer wavelengths passed by the small port 64a.Alternatively, instead of the small long-wavelength port 64a within thewindow 64, a separate long-wavelength port 65 illustrated in FIG. 4Eoutside of the window 64 may be employed and may be made of sapphire orzinc selenide. The long wavelength port 65 may be replaced by itsequivalent, a long wavelength version of the optical fiber 72, such as asapphire optical fiber.

If the sensor 66 is a fluoroptical probe, then it is unaffected by thethermal emissivity of the ring 60. In this case, a fluorescent substanceor powder is immersed in the surface of a small region of the ring 60aligned with the optical fiber end 72b. An optical pulse is appliedperiodically to the other fiber end 72a and the resulting opticalpulse-stimulated emission from the fluorescent powder (in the ring 60)travels from the fiber end 72b to the fiber end 72a to be analyzed bythe sensor 66 to determine the ring temperature. A counterbore in thering 60 shields the optical fiber end 72b from background radiation.

In order to radiantly cool the ring 60, the window 64 may be cooled byconventional means, for example by providing a cold sink for radiantcooling of the polymer-hardening precursor ring 60. In this case, therate at which the polymer-hardening precursor ring 60 is cooled is afunction of [T_(ring) ]⁴ -[T_(window) ]⁴, where T_(ring) and T_(window)are the absolute temperatures (Kelvin), respectively, of thepolymer-hardening precursor ring 60 and the cooled window 64. Efficientradiant cooling of the ring 60 is attained by maintaining a 200° C.temperature difference between the silicon ring 60 and the window 64,which is readily accomplished by conventional liquid or gas coolingapparatus 67 in contact with the window 64, provided the ring 60 ismaintained within the preferred temperature range of 300° C. and 700° C.However, the ring may instead be cooled using any one of a number ofconventional techniques. For example, it may be cooled in the mannerthat the wafer is typically cooled.

Whether the ring 60 is conductively cooled by a conventional cold plateor is radiantly cooled by the window 64, in some cases it may not benecessary to provide a heat source (such as the tungsten halogen lamps).Instead, heating by the plasma itself may be more than sufficient toheat the ring 60, in conjunction with the conductive or radiant cooling,to maintain stable temperature control of the ring 60 within therequisite temperature range. Thus, in an alternative embodiment, no heatsource is provided.

In the embodiment of FIG. 6, the inductive heating coil 62 is replacedby a radiant heater 80 such as a tungsten-halogen lamp or an electricdischarge lamp which emits electromagnetic radiation of a wavelengthwithin the optical transmission band of the quartz window 64 (to avoidheating the window 64) and within the absorption band of thepolymer-hardening precursor ring 60. Preferably, the wavelength of theemission from the radiant heater 80 differs from the wavelength of theemission from the polymer-hardening precursor ring 60 in order to avoidinterfering with the temperature measurement performed by the opticalpyrometer 66. However, if the optical fiber 72 is sunk into thecounterbore 60a and if the optical fiber is completely shielded by theopaque shield 72c that extends down to the top of the counterbore 60a,then the radiant heater emission cannot interfere with the temperaturemeasurement, and so it is not required, in this case, that the radiantheater emission wavelength differ from the emission wavelength of the(silicon) ring 60. In fact, this is advantageous since a number ofcommercially available detectors that could be installed at the outputend of the optical fiber are more stable near the short emissionwavelength range (1-2μ) of silicon. In this case, the temperaturemeasurement is performed at shorter wavelengths so that the longwavelength port 64a or 65 or long wavelength (e.g., sapphire) opticalfiber is not required.

To summarize the requirements for optimum radiant heating and radianttemperature sensing: (a) the material of the window 64 is highlytransmissive at the wavelength of the radiant heat source 80 and eitherthe window 64 itself or a small assigned portion of it or an opticalfiber through it is highly transmissive at the wavelength to which thetemperature sensor 66 is responsive but is not itself highly radiant atthat wavelength; (b) the polymer-hardening precursor ring 60 is highlyabsorbing at the wavelength of the radiant heater 80 and either the ring60 itself or a material embedded in or on it is radiant at thewavelength at which the sensor 66 responds; and (c) the wavelength ofthe radiant heater 80 does not coincide with the wavelength at which thesensor 66 is responsive and yet lies within the absorption spectrum ofthe polymer precursor ring 60 and outside the absorption spectrum of thewindow 64.

The foregoing requirements can be met in various ways, for example byfirst specifying the materials of the polymer-hardening precursor ring60 and then selecting a compatible material for the window 64 and thenfinally selecting the wavelengths of the radiant heater and the sensor66 by process of elimination, or else specifying the wavelengths of thesensor 66 and the radiant heater and then selecting the materials byprocess of elimination. The foregoing requirements may be relaxed to anextent depending upon the sensitivity of the temperature measurement andtemperature control precision desired.

If radiant cooling is desired, then further requirements are imposedupon the window 64: (a) in the portion of the window 64 through whichthe sensor 66 views the ring 60 the window 64 is at least nearlytransparent to the wavelength of radiation emitted by the heated ring 60(as stated above), while (b) in other portions of the window 64 not usedby the sensor 66 to view the ring 60 the window 64 has an absorptionspectrum which includes the re-radiation wavelength of the radiantlyheated polymer-hardening precursor ring 60, so as to absorb heattherefrom to provide radiant cooling.

One way of reducing the number simultaneous constraints on the materialof the window 64 is to not require the window 64 to transmit both heatto the ring 60 and the ring's thermal emission to the sensor 66. This isaccomplished by employing the small long-wavelength (zinc selenide orsapphire) port 64a or auxiliary window 65 for exclusive use by thesensor 66 or to employ the optical fiber 72 for exclusive use by thesensor 66, in either case reducing the function of the window 64 totransmitting radiation from the heat source only. In this case, ifradiant cooling is desired, then the only other constraint on the windowis that it absorb emission from the ring 60. This is possible as long asthe emission wavelength of the radiant heat source 80 and the ringemission are of different wavelengths. Furthermore, it is preferred thatthe sensor 66 is not responsive at the wavelengths emitted by theradiant heat source 80.

In one working example, the polymer-hardening precursor ring 60 wascrystalline silicon with a resistivity of 0.01 Ω-cm and an averageemissivity between 0.3 and 0.7, the window 64 was quartz with an opticalpassband between 300 nm and 3 microns, the sensor 66 was an opticalpyrometer that sensed radiation through an optical fiber (correspondingto the optical fiber 72) in a wavelength range of 4-10 microns and theradiant heater 80 was a 3000° K. tungsten-halogen lamp with a peak poweremission wavelength range of 0.9-1.0 micron. It should be noted thatoptical pyrometry in either a visible or non-visible wavelength rangemay be employed in carrying out the invention.

Referring now to a preferred embodiment illustrated in FIG. 7, anexpendable polymer-hardening precursor ring 60 of silicon is added tothe all-semiconductor (silicon) reactor chamber of FIG. 3 and heated bya heating device 90 which may be either an induction heater or a radiantheater. Optionally, and in addition, a separate RF bias source 400 maybe connected to the ring 60 to help, along with the heating of the ring60, to maintain the ring 60 reactive with the plasma and furnishpolymer-hardening precursor material therefrom into the plasma. Theadvantage is that none of the silicon window electrodes (e.g., thesilicon side wall 12 or the silicon ceiling 14) are used to providesilicon to the polymer chemistry and therefore they need not be heatedto the elevated temperatures (e.g., over 200° C. to 700° C.) to which apolymer-hardening precursor must be heated. Moreover, the RF bias powerapplied to the silicon wall 12 and the silicon ceiling 14 need not be sohigh as to promote consumption of the silicon material thereof. In fact,it may be preferable to apply no bias to the walls and ceiling.Preferably, the temperature of the silicon ceiling 14 and of the siliconside wall 12 and the RF power applied thereto are selected to minimizeconsumption thereof by etching, sputtering or ion bombardment thereofwhile maintaining their surfaces relatively free of polymeraccumulation, to avoid frequent chamber cleaning operations. The bestmode for accomplishing this is the light deposition mode referred tolater in this specification. In a light deposition mode carried outduring a two-minute plasma etch/polymer deposition process, the siliconwall temperature is maintained near 100° C.-150° C., and the resultingpolymer deposition thereon is sufficiently light so that it can beremoved subsequently by a 10 to 20 second exposure to a high densityoxygen plasma temporarily generated in the chamber following etching ofthe wafer. Alternatively, but not preferably, a heavy deposition modemay be employed in which the silicon chamber walls are held near roomtemperature (for example) during the etch process.

Referring to FIG. 8A, separate independently controllablepolymer-hardening precursor rings 61, 63 are placed at different radiallocations relative to the wafer to permit further compensation forradially non-uniform processing conditions. The separate outer and innerpolymer-hardening precursor rings 61, 63 of FIG. 8A are independentlycontrolled by respective temperature controllers 68a, 68b in a mannerdescribed below in this specification. In order to compensate forprocessing conditions giving rise to different etch selectivities atdifferent radial locations on the wafer 17, the user may selectdifferent polymer-hardening precursor ring temperatures to be maintainedby the different temperature controllers 68a, 68b.

While any suitable reactor configuration may be employed in carrying outan embodiment having the separately controlled outer and innerpolymer-hardening precursor rings 61, 63, the implementation illustratedin FIG. 8A employs a reactor having a solenoidal antenna over a heatedsemiconductor window electrode ceiling of the type disclosed inabove-referenced co-pending U.S. application Ser. No. 08/648,254 byKenneth S. Collins et al. entitled "Inductively Coupled RF PlasmaReactor Having Overhead Solenoidal Antenna". Notably, the presentlypreferred implementation of the present invention employs the reactor ofthe above-referenced co-pending application but with only the outerpolymer-hardening precursor ring 61. The reactor of the above-referencedco-pending application includes a cylindrical chamber 140 having anon-planar coil antenna 142 whose windings 144 are closely concentratedin non-planar fashion near the center axis 146 of the cylindricalchamber 140. While in the illustrated embodiment the windings 144 aresymmetrical and have an axis of symmetry coinciding with the center axisof the chamber, the invention may be carried out differently. Forexample, the windings may not be symmetrical and/or their axis ofsymmetry may not coincide with the center of the chamber or theworkpiece center. Close concentration of the windings 144 about thecenter axis 146 is accomplished by vertically stacking the windings 144in the manner of a solenoid so that they are each a minimum distancefrom the chamber center axis 146. This increases the product of current(I) and coil turns (N) near the chamber center axis 146 where the plasmaion density has been the weakest for short workpiece-to-ceiling heights.As a result, the RF power applied to the non-planar coil antenna 142produces greater induction [d/dt] [N·I] near the chamber center axis 146(relative to the peripheral regions) and therefore greater plasma iondensity in that region, so that the resulting plasma ion density is morenearly uniform despite the small workpiece-to-ceiling height. Thus, theinvention provides a way for reducing the ceiling height for enhancedplasma process performance without sacrificing process uniformity.

The cylindrical chamber 140 consists of a cylindrical side wall 150 anda circular ceiling 152 which can be integrally formed with the side wall150 so that the side wall 150 and ceiling 152 can constitute a singlepiece of material, such as silicon. However, the embodiment illustratedFIG. 8A has the side wall 150 and ceiling 152 formed as separate pieces.The circular ceiling 152 may be of any suitable cross-sectional shapesuch as planar, dome, conical, truncated conical, cylindrical or anycombination of such shapes or curve of rotation. Generally, the verticalpitch of the solenoid antenna 142 (i.e., its vertical height divided byits horizontal width) exceeds the vertical pitch of the ceiling 152,even for ceilings defining 3-dimensional surfaces such as dome, conical,truncated conical and so forth. For example, the vertical pitch of thesolenoid antenna 142 is several times the vertical pitch of a typicaldome-shaped ceiling. Of course, the vertical pitch of the flat ceiling152 of FIG. 8A is zero. A solenoid having a pitch exceeding that of theceiling is referred to herein as a non-conformal solenoid, meaning that,in general, its shape does not conform with the shape of the ceiling,and more specifically that its vertical pitch exceeds the vertical pitchof the ceiling.

A pedestal 154 at the bottom of the chamber 140 supports a workpiece156, such as a semiconductor wafer, which is to be processed. Thechamber 140 is evacuated by a pump (not shown in the drawing) through anannular passage 158 to a pumping annulus 160 surrounding the lowerportion of the chamber 140. The interior of the pumping annulus may belined with a replaceable metal liner 160a. The annular passage 158 isdefined by the bottom edge 150a of the cylindrical side wall 150 and thetop surface of the outer silicon ring 61 surrounding. Process gas isfurnished into the chamber 140 through any one or all of a variety ofgas feeds. In order to control process gas flow near the workpiececenter, a center gas feed 164a can extend downwardly through the centerof the ceiling 152 toward the center of the workpiece 156. In order tocontrol gas flow near the workpiece periphery, plural radial gas feeds164b, which can be controlled independently of the center gas feed 164a,extend radially inwardly from the side wall 150 toward the workpieceperiphery, or base axial gas feeds 164c extend upwardly from near thepedestal 154 toward the workpiece periphery, or ceiling axial gas feeds164d can extend downwardly from the ceiling 152 toward the workpieceperiphery. Etch rates at the workpiece center and periphery can beadjusted independently relative to one another to achieve a moreradially uniform etch rate distribution across the workpiece bycontrolling the process gas flow rates toward the workpiece center andperiphery through, respectively, the center gas feed 164a and any one ofthe outer gas feeds 164b-d. This feature of the invention can be carriedout with the center gas feed 164a and only one of the peripheral gasfeeds 164b-d.

The solenoidal coil antenna 142 is wound around a housing 166surrounding the center gas feed 164. A plasma source RF power supply 168is connected across the coil antenna 142 and a bias RF power supply 170is connected to the pedestal 154.

In order that the windings 144 be at least nearly parallel to the planeof the workpiece 156, they preferably are not wound in the usual mannerof a helix but, instead, are preferably wound so that each individualturn is parallel to the (horizontal) plane of the workpiece 156 exceptat a step or transition between turns (from one horizontal plane to thenext).

Confinement of the overhead coil antenna 142 to the center region of theceiling 152 leaves a large portion of the top surface of the ceiling 152unoccupied and therefore available for direct contact with temperaturecontrol apparatus including, for example, plural radiant heaters 172such as tungsten halogen lamps and a water-cooled cold plate 174 whichmay be formed of copper or aluminum for example, with coolant passages174a extending therethrough. Preferably the coolant passages 174acontain a coolant of a known variety having a high thermal conductivitybut a low electrical conductivity, to avoid electrically loading downthe antenna or solenoid 142. The cold plate 174 provides constantcooling of the ceiling 152 while the maximum power of the radiantheaters 172 is selected so as to be able to overwhelm, if necessary, thecooling by the cold plate 174, facilitating responsive and stabletemperature control of the ceiling 152. The large ceiling areairradiated by the heaters 172 provides greater uniformity and efficiencyof temperature control. (It should be noted that radiant heating is notnecessarily required in carrying out the invention, and the skilledworker may choose to employ an electric heating element instead, as willbe described later in this specification.) If the ceiling 152 issilicon, as disclosed in co-pending U.S. application Ser. No. 08/597,577filed Feb. 2, 1996 by Kenneth S. Collins et al., then there is asignificant advantage to be gained by thus increasing the uniformity andefficiency of the temperature control across the ceiling. Specifically,where a polymer precursor and etchant precursor process gas (e.g., afluorocarbon gas) is employed and where the etchant (e.g., fluorine)must be scavenged, the rate of polymer deposition across the entireceiling 152 and/or the rate at which the ceiling 152 furnishes afluorine etchant scavenger material (silicon) into the plasma is bettercontrolled by increasing the contact area of the ceiling 152 with thetemperature control heater 172. The solenoid antenna 142 increases theavailable contact area on the ceiling 152 because the solenoid windings144 are concentrated at the center axis of the ceiling 152.

The increase in available area on the ceiling 152 for thermal contact isexploited in a preferred implementation by a highly thermally conductivetorus 175 (formed of a ceramic such as aluminum nitride, aluminum oxideor silicon nitride or of a non-ceramic like silicon either lightly dopedor undoped) whose bottom surface rests on the ceiling 152 and whose topsurface supports the cold plate 174. One feature of the torus 175 isthat it displaces the cold plate 174 well-above the top of the solenoid142. This feature substantially mitigates or nearly eliminates thereduction in inductive coupling between the solenoid 142 and the plasmawhich would otherwise result from a close proximity of the conductiveplane of the cold plate 174 to the solenoid 142. In order to preventsuch a reduction in inductive coupling, it is preferable that thedistance between the cold plate 174 and the top winding of the solenoid142 be at least a substantial fraction (e.g., one half) of the totalheight of the solenoid 142. Plural axial holes 175a extending throughthe torus 175 are spaced along two concentric circles and hold theplural radiant heaters or lamps 172 and permit them to directlyirradiate the ceiling 152. For greatest lamp efficiency, the holeinterior surface may be lined with a reflective (e.g., aluminum) layer.The ceiling temperature is sensed by a sensor such as a thermocouple 176extending through one of the holes 175a not occupied by a lamp heater172. For good thermal contact, a highly thermally conductive elastomer173 such as silicone rubber impregnated with boron nitride is placedbetween the ceramic torus 175 and the copper cold plate 174 and betweenthe ceramic torus 175 and the silicon ceiling 152.

In the embodiment of FIG. 8A, the chamber 140 may be anall-semiconductor chamber, in which case the ceiling 152 and the sidewall 150 are both a semiconductor material such as silicon. RF biaspower is applied separately to the semiconductor ceiling 152 andsemiconductor wall 150 by respective RF power sources 1210, 1212.Controlling the temperature of, and RF bias power applied to, either theceiling 152 or the wall 150 regulates the extent to which it furnishesfluorine scavenger precursor material (silicon) into the plasma or,alternatively, the extent to which it is coated with polymer. Thematerial of the ceiling 152 is not limited to silicon but may be, in thealternative, silicon carbide, silicon dioxide (quartz), silicon nitrideor a ceramic.

The chamber wall or ceiling 150, 152 need not be used as the source of afluorine scavenger material. Instead, a disposable silicon member can beplaced inside the chamber 140 and maintained at a sufficiently hightemperature to prevent polymer condensation thereon and permit siliconmaterial to be removed therefrom into the plasma as fluorine scavengingmaterial. In this case, the wall 150 and ceiling 152 need notnecessarily be silicon, or if they are silicon they may be maintained ata temperature (and/or RF bias) near or below the polymer condensationtemperature (and/or a polymer condensation RF bias threshold) so thatthey are coated with polymer from the plasma so as to be protected frombeing consumed. While the disposable silicon member may take anyappropriate form, in the embodiment of FIG. 8A the outer and innersilicon ring pieces 61, 63 may be removable and disposable expendablemembers of high purity silicon and may be doped to alter theirelectrical or optical properties. In order to maintain the silicon rings61, 63 at a sufficient temperatures to ensure their favorableparticipation in the plasma process (e.g., its contribution of siliconmaterial into the plasma for fluorine scavenging), respective sets 177a,177b of plural radiant (e.g., tungsten halogen lamp) heaters arranged ina circle under the silicon ring 61 and over the silicon ring 63,respectively heat the respective rings 61, 63 through respective quartzwindows 178a, 178b. The respective sets of heaters 177a, 177b arecontrolled in accordance with the temperature of the respective siliconrings 61, 63 sensed by respective temperature sensors 179a, 179b whichmay be remote sensors such as optical pyrometers or fluoro-opticalprobes. The sensors 179a, 179b may extend partially into deep holes inthe respective rings 61, 63, the deepness and narrowness of the holetending at least partially to mask temperature-dependent variations inthermal emissivity of the silicon rings 61, 63, so that they appear tobehave more like gray-body radiators for more reliable temperaturemeasurement.

As described in U.S. application Ser. No. 08/597,577 referred to above,an advantage of an all-semiconductor chamber is that the plasma is freeof contact with contaminant producing materials such as metal, forexample. For this purpose, plasma confinement magnets 180, 182 adjacentthe annular opening 158 prevent or reduce plasma flow into the pumpingannulus 160. To the extent any polymer precursor and/or active speciessucceeds in entering the pumping annulus 160, any resulting polymer orcontaminant deposits on the replaceable interior liner 160a may beprevented from re-entering the plasma chamber 140 by maintaining theliner 160a at a temperature significantly below the polymer condensationtemperature, for example, as disclosed in the referenced co-pendingapplication.

A wafer slit valve 184 through the exterior wall of the pumping annulus160 accommodates wafer ingress and egress. The annular opening 158between the chamber 140 and pumping annulus 160 is larger adjacent thewafer slit valve 184 and smallest on the opposite side by virtue of aslant of the bottom edge 150a of the cylindrical side wall 150 so as tomake the chamber pressure distribution more symmetrical with anon-symmetrical pump port location.

A second outer vertical stack or solenoid 1120 of windings 1122 at anouter location (i.e, against the outer circumferential surface of thethermally conductive torus 175) is displaced by a radial distance δRfrom the inner vertical stack of solenoidal windings 144. Note thatconfinement of the inner solenoidal antenna 142 to the center and theouter solenoidal antenna 1120 to the periphery leaves a large portion ofthe top surface of the ceiling 152 available for direct contact with thetemperature control apparatus 172, 174, 175. An advantage is that thelarger surface area contact between the ceiling 152 and the temperaturecontrol apparatus provides a more efficient and more uniform temperaturecontrol of the ceiling 152.

For a reactor in which the side wall and ceiling are formed of a singlepiece of silicon for example with an inside diameter of 12.6 in (32 cm),the wafer-to-ceiling gap is 3 in (7.5 cm), and the mean diameter of theinner solenoid was 3.75 in (9.3 cm) while the mean diameter of the outersolenoid was 11.75 in (29.3 cm) using 3/16 in diameter hollow coppertubing covered with a 0.03 thick teflon insulation layer, each solenoidconsisting of four turns and being 1 in (2.54 cm) high. The outer stackor solenoid 1120 is energized by a second independently controllableplasma source RF power supply 196. The purpose is to permit differentuser-selectable plasma source power levels to be applied at differentradial locations relative to the workpiece or wafer 156 to permitcompensation for known processing non-uniformities across the wafersurface, a significant advantage. In combination with the independentlycontrollable center gas feed 164a and peripheral gas feeds 164b-d, etchperformance at the workpiece center may be adjusted relative to etchperformance at the edge by adjusting the RF power applied to the innersolenoid 142 relative to that applied to the outer solenoid 1120 andadjusting the gas flow rate through the center gas feed 164a relative tothe flow rate through the outer gas feeds 164b-d. While the presentinvention solves or at least ameliorates the problem of a center null ordip in the inductance field as described above, there may be otherplasma processing non-uniformity problems, and these can be compensatedin the versatile embodiment of FIG. 8A by adjusting the relative RFpower levels applied to the inner and outer antennas. For effecting thispurpose with greater convenience, the respective RF power supplies 168,196 for the inner and outer solenoids 142, 1120 may be replaced by acommon power supply and a power splitter which can be variable to permitthe user to change the relative apportionment of power between the innerand outer solenoids 142, 1120 while preserving a fixed phaserelationship between the fields of the inner and outer solenoids 142,1120. This is particularly important where the two solenoids 142, 1120receive RF power at the same frequency. Otherwise, if the twoindependent power supplies 168, 196 are employed, then they may bepowered at different RF frequencies, in which case it is preferable toinstall RF filters at the output of each RF power supply 168, 196 toavoid off-frequency feedback from coupling between the two solenoids. Inthis case, the frequency difference should be sufficient to time-averageout coupling between the two solenoids and, furthermore, should exceedthe rejection bandwidth of the RF filters. Another option is to makeeach frequency independently resonantly matched to the respectivesolenoid, and each frequency may be varied to follow changes in theplasma impedance (thereby maintaining resonance) in lieu of conventionalimpedance matching techniques. In such implementations, the frequencyranges of the two solenoids should be mutually exclusive. Preferably,however, the two solenoids are driven at the same RF frequency and inthis case it is preferable that the phase relationship between the twobe such as to cause constructive interaction or superposition of thefields of the two solenoids 142, 1120. Generally, this requirement willbe met by a zero phase angle between the signals applied to the twosolenoids if they are both wound in the same sense. Otherwise, if theyare oppositely wound, the phase angle is preferably 180°. In any case,coupling between the inner and outer solenoids can be minimized oreliminated by having a relatively large space between the inner andouter solenoids 142, 1120.

The range attainable by such adjustments is increased by increasing theradius of the outer solenoid 1120 to increase the spacing between theinner and outer solenoids 142, 1120, so that the effects of the twosolenoids 142, 1120 are more confined to the workpiece center and edge,respectively. This permits a greater range of control in superimposingthe effects of the two solenoids 142, 1120. For example, the radius ofthe inner solenoid 142 should be no greater than about half theworkpiece radius and preferably no more than about a third thereof. (Theminimum radius of the inner solenoid 142 is affected in part by thediameter of the conductor forming the solenoid 142 and in part by theneed to provide a finite non-zero circumference for an arcuate--e.g.,circular--current path to produce inductance.) The radius of the outersolenoid 1120 should be at least equal to the workpiece radius andpreferably 1.5 or more times the workpiece radius. With such aconfiguration, the respective center and edge effects of the inner andouter solenoids 142, 1120 are so pronounced that by increasing power tothe inner solenoid the chamber pressure can be raised into the hundredsof mT while providing a uniform plasma, and by increasing power to theouter solenoid 1120 the chamber pressure can be reduced to on the orderof 0.01 mT while providing a uniform plasma. Another advantage of such alarge radius of the outer solenoid 1120 is that it minimizes couplingbetween the inner and outer solenoids 142, 1120.

In the embodiment of FIG. 8A, the ceiling 152 and side wall 150 areseparate semiconductor (e.g., silicon) pieces insulated from one anotherhaving separately controlled RF bias power levels applied to them fromrespective RF sources to enhance control over the center etch rate andselectivity relative to the edge. As set forth in greater detail inabove-referenced U.S. application Ser. No. 08/597,577 filed Feb. 2, 1996by Kenneth S. Collins et al., the ceiling 152 may be a semiconductor(e.g., silicon) material doped so that it will act as an electrodecapacitively coupling the RF bias power applied to it into the chamberand simultaneously as a window through which RF power applied to thesolenoid 142 may be inductively coupled into the chamber. The advantageof such a window-electrode is that an RF potential may be establisheddirectly over the wafer (e.g., for controlling ion energy) while at thesame time inductively coupling RF power directly over the wafer. Thislatter feature, in combination with the separately controlled inner andouter solenoids 142, 1120 and center and peripheral gas feeds 164a, 164bgreatly enhances the ability to adjust various plasma process parameterssuch as ion density, ion energy, etch rate and etch selectivity at theworkpiece center relative to the workpiece edge to achieve an optimumuniformity. In this combination, the respective gas flow rates throughindividual gas feeds are individually and separately controlled toachieve such optimum uniformity of plasma process parameters.

The lamp heaters 172 may be replaced by electric heating elements.

FIG. 8B illustrates another variation in which the ceiling 152 itselfmay be divided into an inner disk 152a and an outer annulus 152belectrically insulated from one another and separately biased byindependent RF power sources 1214, 1216 which may be separate outputs ofa single differentially controlled RF power source.

In accordance with an alternative embodiment, a user-accessible centralcontroller 300 shown in FIGS. 8A and 8B, such as a programmableelectronic controller including, for example, a conventionalmicroprocessor and memory, is connected to simultaneously control gasflow rates through the central and peripheral gas feeds 164a, 164, RFplasma source power levels applied to the inner and outer antennas 142,1120 and RF bias power levels applied to the ceiling 152 and side wall150 respectively (in FIG. 8A) and the RF bias power levels applied tothe inner and outer ceiling portions 152a, 152b (in FIG. 8B),temperature of the ceiling 152 and the temperature of the silicon rings61, 63.

A ceiling temperature controller 1218 governs power applied to theceiling heater lamps 172 by comparing the temperature measured by theceiling temperature sensor 176 with a commanded target temperature forthe ceiling 152 (received from the programmable controller 300).Similarly, the outer silicon ring temperature controller 68a governspower applied to the heater lamps 177a underlying the outer silicon ring61 by comparing the temperature measured by the outer ring temperaturesensor 179a with a commanded target temperature for the outer ring 61(received from the programmable controller 300). Likewise, the innersilicon ring temperature controller 68b governs power applied to theheater lamps 177b overlying the inner silicon ring 63 by comparing thetemperature measured by the inner ring temperature sensor 179b with acommanded target temperature for the inner silicon ring 63 (receivedfrom the programmable controller 300). The programmable controller 300governs the target temperatures of the silicon ring temperaturecontrollers 68a and 68b, the ceiling temperature controller 1218, the RFpower levels of the solenoid power sources 168, 196, the RF power levelsof the bias power sources 1210, 1212 (FIG. 8A) or 1214, 1216 (FIG. 8B),the wafer bias level applied by the RF power source 170 and the gas flowrates supplied by the various gas supplies (or separate valves) to thegas inlets 164a-d. The key to controlling the wafer bias level is the RFpotential difference between the wafer pedestal 154 and the ceiling 152.Thus, either the pedestal RF power source 170 or the ceiling RF powersource 1212 may be a short to RF ground. With the programmablecontroller 300, the user can easily optimize apportionment of RF sourcepower, RF bias power, silicon emission and gas flow rate at theworkpiece center relative to the workpiece periphery to achieve thegreatest center-to-edge process uniformity across the surface of theworkpiece (e.g., uniform radial distribution of etch rate and etchselectivity). Also, by adjusting (through the controller 300) the RFpower applied to the solenoids 142, 1120 relative to the RF powerdifference between the pedestal 154 and ceiling 152, the user canoperate the reactor in a predominantly inductively coupled mode or in apredominantly capacitively coupled mode.

While the various power sources connected in FIG. 8A to the solenoids142, 1120, the ceiling 152, side wall 150 (or the inner and outerceiling portions 152a, 152b as in FIG. 8B) have been described asoperating at RF frequencies, the invention is not restricted to anyparticular range of frequencies, and frequencies other than RF may beselected by the skilled worker in carrying out the invention.

In a preferred embodiment of the invention, the high thermalconductivity spacer 175, the ceiling 152 and the side wall 150 areintegrally formed together from a single piece of crystalline silicon.

While the expendable polymer-hardening precursor piece has beendescribed as a planar ring (60 in FIGS. 6 and 7 and 61 in FIGS. 8A and8B) in the wafer support pedestal top surface plane, it may be of anyshape and at any location, provided that it is not too distant from theheat source to be efficiently heated thereby and provided that itshields the plasma processing region of the chamber from the heat source(so as to avoid diversion of power from the heat source to plasmageneration in the chamber). In the preferred embodiment some shieldingof the plasma from energy of the heat source (in addition to thatprovided by the silicon ring 60 itself) is provided by a pair of ringmagnets 100, 102 that prevent plasma flow between the plasma processingregion of the chamber and the pumping annulus.

Another embodiment that provides the requisite shielding and closeproximity of the expendable polymer-hardening precursor piece to aremote heat source is illustrated in FIG. 9 in which the expendablepiece is a cylindrical silicon liner 210 abutting the cylindricalchamber side wall interior surface. A peripheral heat source 215adjacent the outside of the cylindrical side wall heats the siliconliner 210 through the side wall. The peripheral heat source 215 may bean induction heater, in which case the cylindrical chamber wall iseither an insulator such as quartz or is a semiconductor such as siliconof sufficiently high resistivity to minimize absorption and maximizetransmission of the induction field of the heat source 215 to the liner210. Alternatively, the peripheral heat source 215 is a radiant heatersuch as a tungsten halogen lamp or an electric discharge lamp. Atemperature sensor 266 and temperature controller 268 governingoperation of the peripheral heater 215 perform temperature control. Inthe embodiment of FIG. 9, the master controller 300 governs thetemperature controller 168.

The graph of FIG. 10 illustrates the performance of a temperaturecontrol system implemented in the embodiment of FIG. 6. The horizontalaxis is the steady state temperature in degrees Celsius at which thetemperature controller 68 has been commanded to hold the silicon ring60, while the vertical axis is the applied power in Watts required tomaintain the selected ring temperature. The graph of FIG. 11 illustratesthe closed loop temperature response of the system of FIG. 6, thehorizontal axis being time in seconds and the vertical axis being thering temperature in degrees Celsius. In the graph of FIG. 11, the ring60 begins at an initial temperature near room temperature and, afterabout 30 seconds, the controller 68 is commanded to put the ringtemperature at 440° C. This temperature is reached at about 310 secondswith no overshoot and only a trace amount of system noise. At about 550seconds a plasma is ignited in the chamber and is extinguished at about1000 seconds, the effect on the ring temperature being almostunobservable in FIG. 11. This latter event proves the stability of thetemperature control system and its responsiveness. FIG. 12 is a greatlyenlarged view of a portion of the graph of FIG. 11 in the neighborhoodof the time window from 301 seconds (when the target temperature isreached with no overshoot) and including 550 seconds (when the plasma istemporarily turned on). The plasma was ignited with 3.2 kwatts of sourcepower at 550 seconds and the enlarged view of FIG. 12 reveals a shortspike in the ring temperature coincident with that event. This data wasobtained using the fluoro-optical probe version of the sensor 66 and theoptical fiber 72.

In lieu of heating the polymer hardening precursor piece (e.g., thesilicon ring 60), RF bias power may be applied from a source 400(indicated in dashed line in FIG. 7) to the silicon ring 60 to achieve adesired effect in increasing polymer resistance to etching. The skilledworker can readily ascertain the requisite RF bias power level for thisapplication by increasing the RF bias power on the piece (e.g., thesilicon ring 60) to a threshold level at which polymer deposition nolonger accumulates on the piece so that the surface of the piece remainsfree for interaction with the plasma. Furthermore, increasing the RFbias power applied to the piece (e.g., the silicon ring 60) beyond thisthreshold level actually increases the polymer hardness on the wafer andconsequently increases the etch selectivity beyond that achieved at thethreshold RF bias power level. While this may be practiced as analternative mode of the invention, it is not the most preferable modebecause: (a) the consumption of the polymer hardening precursor piecewill be higher, and (b) some electrical (RF) coupling to the polymerhardening precursor piece must be provided to impose the requisite RFbias power on it, complicating its structure. In yet another alternativemode, heating and RF biasing of the polymer hardening precursor piecemay be combined.

While the invention has been described as being carried out with anumber of separate RF sources, some or all of the RF sources depictedherein may derive their outputs from separate RF generators or from acommon RF generator with different outputs at different RF power levels,frequencies and phases synthesized with variable power dividers,frequency multipliers and/or phase delays, as may be appropriate.Moreover, while the invention has been described as being carried outwith a number of separate process gas supplies, some or all of theprocess gas supplies may be derived from a common process gas supplywhich is divided among the plural separately controlled gas inlets 64.

While the invention has been described in detail by specific referenceto preferred embodiments thereof, it is understood that variations andmodifications thereof may be made without departing from the true spiritand scope of the invention.

What is claimed is:
 1. A plasma etch process comprising:providing achamber within which to carry out said process; supporting an article tobe processed on a support in the chamber; supplying a process gascontaining at least etchant and polymer precursor materials; providing,in addition to said process gas, a source material of silicon or carbonin said chamber; generating a plasma within said chamber; maintainingsaid source material at a temperature greater than that temperaturerequired to scavenge fluorine.
 2. The process of claim 1 wherein thestep of maintaining comprises heating said source material to at least apolymer condensation temperature.
 3. The process of claim 2 wherein saidetch process etches first and second different materials on said articleat first and second etch rates respectively, said first etch rate beinggreater than said second etch rate corresponding to an etch selectivityof said first material to said second material which is a function ofsaid first and second etch rates, and wherein said maintaining stepfurther comprises:increasing a temperature of said source material intoa temperature range above said polymer condensation temperature toincrease said etch selectivity.
 4. The process of claim 3 wherein saidfirst material overlies said second material and said etchant createsopenings through said first material to a expose portions of said secondmaterial.
 5. The process of claim 4 wherein:said polymer precursormaterial provides material for polymer deposition on the exposedportions of said second material; said etchant precursor materialprovides material for etching said article; and said polymer depositionreduces etching of said second material to enhance etch selectivity. 6.The process of claim 5 wherein:a photoresist mask layer over said firstmaterial has openings therethrough defining said openings; and saidpolymer deposition reduces etching of said second material and of saidphotoresist material to enhance etch selectivity.
 7. The process ofclaim 5 wherein said first material comprises an oxygen-containingmaterial and said second material comprises a non-oxygen containingmaterial.
 8. The process of claim 2 wherein said maintaining stepfurther comprises:increasing a temperature of said source material intoa temperature range above said polymer condensation temperature.
 9. Theprocess of claim 8 wherein said temperature range is one wherein polymerformed on said wafer contains an amount of said source material.
 10. Theprocess of claim 8 wherein said temperature range lies above about 100°C.
 11. The process of claim 8 wherein said temperature range lies aboveabout 220° C.
 12. The process of claim 9 wherein said temperature rangelies above about 100° C.
 13. The process of claim 9 wherein saidtemperature range lies above 220° C.
 14. The process of claim 3 whereinsaid temperature range lies above about 100° C.
 15. The process of claim3 wherein said temperature range lies above about 220° C.
 16. Theprocess of claim 3 wherein said first material comprises an oxide, saidsecond material comprises silicon or polysilicon, an etchant precursorof said process gas comprises fluorine, an polymer precursor of saidprocess gas comprises at least fluorine and carbon and said sourcematerial comprises silicon.
 17. The process of claim 16 furthercomprising applying RF power to said source material at an RF powerlevel substantially reduced from a reference power level at which saidsource material when near said polymer condensation temperature providesa significant amount of fluorine scavenger material into said plasma,while increasing the temperature of said source material to compensatefor the reduction in RF power.
 18. The process of claim 17 wherein saidRF power level is reduced by at least an integer number below saidreference power level while said target temperature is only fractionallyincreased.
 19. The process of claim 18 wherein said RF power level isreduced about four-fold and said target temperature is increased toabout 240° C.
 20. The process of claim 3 wherein said temperature rangelies between about 180° C. and 220° C.
 21. The process of claim 3wherein said temperature range lies between about 300° C. and 700° C.22. The process of claim 3 wherein said temperature range lies betweenabout 240° C. and 500° C.
 23. The process of claim 1 further comprisingapplying RF power to said source material.
 24. The process of claim 23wherein said source material comprises a scavenger for an etchantderived from said etchant precursor, and wherein said RF power appliedto said source material is sufficient to promote significant scavengingof said etchant.
 25. The process of claim 3 wherein said etchselectivity is at least 110:1.
 26. The process of claim 3 wherein saidtemperature range lies between about 500° C. and 700° C. and said etchselectivity is at least 150:1.
 27. The process of claim 3 wherein aphotoresist selectivity of said first material to said second materialis at least 3:1.
 28. The process of claim 3 wherein said temperaturerange lies between about 400° C. and 700° C. and a photoresistselectivity of said first material to said second material is at least5:1.
 29. The process of claim 2 wherein the step of maintaining furthercomprises using said source material to change a process gas contentratio such that a substantially strengthened polymer is formed.
 30. Theprocess of claim 29 wherein said process gas content ratio includes atleast one of: (a) carbon-to-fluorine; (b) hydrogen-to-fluorine; and (c)carbon-to-hydrogen.
 31. A plasma etch process comprising:providing achamber within which to carry out said process; supporting an article tobe processed on a support in the chamber; supplying a process gascontaining at least etchant and polymer precursor materials; providing apolymer-hardening precursor material in said chamber; generating aplasma within said chamber; maintaining said precursor material at atemperature greater than that temperature required to scavenge fluorine.32. The process of claim 31 wherein the step of maintaining comprisesheating said precursor material to at least a polymer condensationtemperature.
 33. The process of claim 32 wherein said maintaining stepcomprises heating said polymer-hardening precursor material to atemperature range above said polymer condensation temperature.
 34. Theprocess of claim 33 wherein said temperature range is such that polymerformed on said wafer comprises material from said polymer-hardeningprecursor material.
 35. The process of claim 33 wherein said firstmaterial comprises an oxide, said second material comprises silicon orpolysilicon, said etchant precursor of said process gas comprisesfluorine, said polymer precursor of said process gas comprises at leastfluorine and carbon and said polymer-hardening precursor materialcomprises silicon.
 36. The process of claim 33 wherein said temperaturerange lies above about 100° C.
 37. The process of claim 33 wherein saidtemperature range lies above 220° C.
 38. The process of claim 31 whereinsaid etch process etches first and second different materials on saidarticle at first and second etch rates respectively, said first etchrate being greater than said second etch rate corresponding to an etchselectivity of said first material to said second material which is afunction of said first and second etch rates, and wherein saidmaintaining step further comprises:increasing a temperature of saidpolymer-hardening precursor material to a temperature range above saidpolymer condensation temperature to achieve a corresponding increasesaid etch selectivity.
 39. The process of claim 38 wherein said firstmaterial overlies said second material and said etchant creates openingsthrough said first material to a expose portions of said secondmaterial.
 40. The process of claim 39 wherein:said polymer precursormaterial provides material for polymer deposition on the exposedportions of said second material; said etchant precursor materialprovides material for etching said article; and said polymer depositionreduces etching of said second material to enhance etch selectivity. 41.The process of claim 40 wherein:a photoresist mask layer over said firstmaterial has openings therethrough defining said openings; and saidpolymer deposition reduces etching of said second material and of saidphotoresist material to enhance etch selectivity.
 42. The process ofclaim 40 wherein said first material comprises an oxygen-containingmaterial and said second material comprises a non-oxygen containingmaterial.
 43. The process of claim 38 wherein said temperature rangelies above about 100° C.
 44. The process of claim 38 wherein saidtemperature range lies above 220° C.
 45. The process of claim 38 whereinsaid temperature range lies between about 180° C. and 220° C.
 46. Theprocess of claim 28 wherein said temperature range lies between about300° C. and 700° C.
 47. The process of claim 38 wherein said temperaturerange lies between about 240° C. and 500° C.
 48. The process of claim 31further comprising applying RF power to said polymer-hardening precursormaterial.
 49. The process of claim 48 wherein said polymer-hardeningprecursor material comprises a scavenger for an etchant derived fromsaid etchant precursor, and wherein said RF power applied to saidpolymer-hardening precursor material is sufficient to promotesignificant scavenging of said etchant.
 50. The process of claim 31further comprising applying RF power to said polymer-hardening precursormaterial.
 51. The process of claim 50 wherein said RF power is appliedto said polymer-hardening precursor material at an RF power levelsubstantially reduced from a reference power level at which saidpolymer-hardening precursor material provides a significant amount offluorine scavenger material into said plasma near said polymercondensation temperature, while increasing said target temperature tocompensate for the reduction in RF power.
 52. The process of claim 51wherein said RF power level is reduced by at least an integer numberbelow said reference power level while said target temperature is onlyfractionally increased.
 53. The process of claim 51 wherein said RFpower level is reduced approximately four-fold below said referencepower level while said target temperature is increased to on the orderof about 240° C.
 54. The process of claim 31 wherein saidpolymer-hardening precursor material is a member of a class of materialscomprising silicon, carbon, silicon carbide and silicon nitride.
 55. Theprocess of claim 31 wherein the step of providing said polymer-hardeningprecursor material comprises providing a quickly removable piece of saidpolymer-hardening precursor material separate from integral structuresof said reactor chamber.
 56. The process of claim 55 wherein the step ofheating comprises one of: (a) inductively heating and (b) radiantlyheating.
 57. The process of claim 56 wherein the step of maintainingfurther comprises controlling a temperature of said polymer-hardeningprecursor material to a selected temperature by measuring saidtemperature by sensing radiation from said polymer-hardening precursormaterial and heating said precursor material so as to maintain themeasured temperature near said selected temperature.
 58. The process ofclaim 57 wherein the step of measuring comprises remotely sensingradiation from said polymer-hardening precursor material through a port,and the step of heating comprises heating said polymer-hardeningprecursor material through a window, wherein said port is one of: (a) aportion of said window, (b) separate from said window.
 59. The processof claim 58 wherein the step of maintaining comprises radiating heat ata wavelength for which said window is at least nearly transmissive andwherein the step of measuring temperature comprises sensing radiationfrom said polymer-hardening precursor material at a wavelength at whichsaid port is at least nearly transmissive.
 60. A plasma etch processcomprising:providing a chamber within which to carry out said process;supporting an article to be processed on a support in the chamber;supplying a process gas containing at least etchant and polymerprecursor materials; generating a plasma within said chamber; providing,in addition to said process gas, a source material of silicon or carbonin said chamber; applying RF bias power to said source material to atleast maintain said source material at a temperature greater than thattemperature required to scavenge fluorine.
 61. The process of claim 60wherein said etch process etches first and second different materials onsaid article at first and second etch rates respectively, said firstetch rate being greater than said second etch rate corresponding to anetch selectivity of said first material to said second material which isa function of said first and second etch rates.
 62. The process of claim61 wherein said first material overlies said second material and saidetchant creates openings through said first material to a exposeportions of said second material.
 63. The process of claim 62wherein:said polymer precursor material provides material for polymerdeposition on the exposed portions of said second material; said etchantprecursor material provides material for etching said article; and saidpolymer deposition reduces etching of said second material to enhanceetch selectivity.
 64. The process of claim 63 wherein:a photoresist masklayer over said first material has openings therethrough defining saidopenings; and said polymer deposition reduces etching of said secondmaterial and of said photoresist material to enhance etch selectivity.65. The process of claim 63 wherein said first material comprises anoxygen-containing material and said second material comprises anon-oxygen containing material.
 66. A plasma etch processcomprising:providing a chamber within which to carry out said process;supporting an article to be processed on a support in the chamber;supplying a process gas containing at least etchant and polymerprecursor materials; generating a plasma within said chamber; providing,in addition to said process gas, a source material of apolymer-hardening precursor in said chamber; applying RF bias power tosaid source material to at least maintain said source material at atemperature greater than that temperature required to scavenge fluorine.67. The process of claim 66 wherein said etch process etches first andsecond different materials on said article at first and second etchrates respectively, said first etch rate being greater than said secondetch rate corresponding to an etch selectivity of said first material tosaid second material which is a function of said first and second etchrates.
 68. The process of claim 67 wherein said first material overliessaid second material and said etchant creates openings through saidfirst material to a expose portions of said second material.
 69. Theprocess of claim 68 wherein:said polymer precursor material providesmaterial for polymer deposition on the exposed portions of said secondmaterial; said etchant precursor material provides material for etchingsaid article; and said polymer deposition reduces etching of said secondmaterial to enhance etch selectivity.
 70. The process of claim 69wherein:a photoresist mask layer over said first material has openingstherethrough defining said openings; and said polymer deposition reducesetching of said second material and of said photoresist material toenhance etch selectivity.
 71. The process of claim 69 wherein said firstmaterial comprises an oxygen-containing material and said secondmaterial comprises a non-oxygen containing material.